Edited: I read this post second time and I read your comments and now I understood what you meant. I was wrong about calculations.
So, they calculate price of Steem by USD in payments. Now I understood better, thank you for information. I'm enlightened. I understood:
Author payment/2 = SBD reward
Author payment/(2xSteem price) = Steem Power reward
I knew SBD reward calculation, but I had no idea about Steem Power reward calculation. I'm so thankful for this information, I still learn every day lol
I'm sorry for confusing people.